Polyimides generally have high thermal stability and excellent mechanical properties. Uses for this class of polymers include high temperature molding resins, fibers, films, and composite applications. Although there are a number of applications, the development of polyimides has been retarded because they are often difficult to process. Polyimides made from diether dianhydrides have good processability, but their glass transition temperatures (Tg's) are too low for many high performance applications. Copolyimides containing both diether dianhydrides and other dianhydrides such as pyromellitic dianhydride have been shown to have higher glass transition temperatures than do homopolyimides containing only the diether dianhydrides. However, these copolyimides are often insoluble in conventional solvents, such as N-methylpyrrolidinone (NMP), which limit their utility in fiber, film, and composite applications where the solubility of the polyimide is advantageous.
The polyetherimide copolyimides of the present invention can be prepared as the reaction product of 2,2-bis(3,4-dicarboxyphenyl)propane (IPAN), one or more aromatic bis(ether anhydrides), and one or more diamines. The polyetherimides of the present invention have higher glass transition temperatures (Tg's) than polymers made from diether dianhydrides and diamines alone and have better solubility in conventional solvents, such as NMP, than copolyimides made from mixtures of diether dianhydrides and other dianhydrides such as pyromellitic dianhydride. In addition, the copolyimides of this invention are mechanically compatible with other engineering resins.